Did they ever ship a Learjet with an 8-track system for playing music in-flight? Wikipedia's entry doesn't mention using it in aviation, just home audio and—of course—automobiles:
> Intrigued by Earl Muntz’s four-track cartridge, Lear wanted a tape system for his Learjet business aircraft. Realizing that the aviation market was too small, Lear convinced Ford and GM to offer optional 8-track players.
Source: https://americanhistory.si.edu/collections/search/object/nma...
btw, many 8-track tape cartridges had "Lear Jet" embossed in the plastic like this one http://fieldwoodhs.ednet.ns.ca/slim-182dvs10584jet.jpg